It is common practice to secure metal roofing material to thin metal battens by means of self-tapping threaded fasteners of the kind having a drilling tip. Selection of such a fastener from the available range of such fasteners is largely determined by the speed with which the fastening operation can be achieved, but the security or strength of the fastened assembly may be compromised in the process. Fastenings of the aforementioned kind have been found to fail particularly in situations involving relatively high wind loading. It has been discovered that such failures are due at least in part to the distorting effect of the thread form of conventional fasteners on the thin metal battens.